Cutter-suction dredgers (“CSD”) are vessels which can be used to cut and loosen material which is at least partly underwater. This cut material can then be sucked into a suction tube. CSD's are often used to cut hard surface materials, such as rock, although they may also be used to excavate gravel or sand.
CSD's typically use a suction tube with a cutter head at the suction inlet. The cutter head may be connected to the dredger with a hub that is mounted on an axis with a drive to rotate the cutter head. The axis of rotation is referred to as the axial direction of the cutter head. The cutter head and suction inlet may be moveable with respect to the water bed being dredged. In order to draw the material into the suction tube, a wear-resistant pump may be provided, for example, a centrifugal pump. The material cut by the cutter head that has been drawn into the suction tube may then be transported away from the CSD, for example, by a floating pipe line to a dumping location.
A typical cutter head includes a base ring around the suction opening and a hub. The hub and base ring are connected by a plurality of arms extending in an axial direction. The arms may be curved in a tangential and radial direction such that the arms spiral toward each other. In other cutter heads, the arms may be curved in the radial direction only, while being axially aligned or at a small angle with respect to the axial direction. Each arm must be connected to the base ring and to the hub, typically by welding.
The cutter head may additionally be provided with different excavating tools, for example, teeth in the shape of chisels or another shape to assist in the excavation. The teeth can be attached to the arms.
WO2011003869 discloses an example of a cutter head for dredging ground under water. This cutter head is suitable for attachment rotatably around a central axis to a cutter suction dredger and can be moved through the ground therewith in a lateral sweeping movement. The cutter head is formed from support arms which extend spirally between a base ring and a hub located at a distance from the base ring. The support arms are connected to the base ring and to the hub.